Stack - Data Structure

What is a Stack?

A stack is a linear data structure that follows the Last In First Out (LIFO) principle. This means that the last element added to the stack will be the first one to be removed.

Stack Operations

• Push: Add an element to the top of the stack.
• Pop: Remove and return the element from the top of the stack.
• Peek: Return the top element without removing it.
• Is Empty: Check if the stack is empty.
• Is Full (if size limit is set): Check if the stack is full.

Python Code Example for Stack

class Stack:
    def __init__(self):
        self.stack = []

    def push(self, item):
        self.stack.append(item)
        print(f"Pushed {item} to the stack.")

    def pop(self):
        if not self.is_empty():
            return self.stack.pop()
        else:
            return "Stack is empty!"

    def peek(self):
        if not self.is_empty():
            return self.stack[-1]
        else:
            return "Stack is empty!"

    def is_empty(self):
        return len(self.stack) == 0

    def display(self):
        print("Stack: ", self.stack)

# Example usage
my_stack = Stack()
my_stack.push(10)
my_stack.push(20)
my_stack.display()
print(f"Popped item: {my_stack.pop()}")
print(f"Top item: {my_stack.peek()}")
my_stack.display()

            

Time and Space Complexity

• Push: O(1) - constant time.
• Pop: O(1) - constant time.
• Peek: O(1) - constant time.
• Space Complexity: O(n) - where n is the number of elements in the stack.

Visualization of Stack Operations